Wireless communication networks are ubiquitous in many parts of the world. A modern wireless communication network is, in many respects, a complex dynamic system, in which system parameters are constantly monitored and adjusted, to attempt optimal operation in the face of changes in traffic load, usage patterns, channel quality, and other dynamic factors.
In early-generation wireless communication networks (e.g., Wideband Code Division Multiple Access, or WCDMA and Global System for Mobile communications, or GSM), voice services were delivered over circuit switched (CS) domains. CS networks provide guaranteed transport services for voice traffic, which is very sensitive to packet-level transmission characteristics, such as delay and loss or jitter. The Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) was originally designed for high speed data transfer, and does not include circuit switched domains. Still, there is a strong motivation to support voice service over LTE networks. Voice over LTE (VoLTE) is much more bandwidth efficient than WCDMA and GSM voice. Once a good LTE coverage is achieved, the older network technologies (e.g., WCDMA and GSM) can be phased out and the frequency bands can be reused for newer, more efficient network technologies. LTE networks span numerous domains, or technologies, each optimized for different aspects of communication network operation.
FIG. 1 depicts a diagram of some relevant nodes in an LTE network 10, grouped into three domains: the Radio Access Network (RAN) domain 14, the Evolved Packet Core (EPC) domain 20, and the IP Multimedia Subsystem (IMS) domain 40.
The radio access network (RAN) provides wireless connectivity between a large number of (possibly mobile) User Equipment (UE) 12, such as smartphones, machine-to-machine (M2M) devices, laptop or tablet computers, and the like, and fixed terrestrial base stations (E-NodeB, or eNB) 16a, 16b. 
The LTE RAN 14, e.g., Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial RAN, or E-UTRAN, is connected to the Evolved Packet Core (EPC) domain 20. EPC 20 is an IP-based multiservice core network providing end-to-end service delivery for user traffic and ensuring signaling-based mobility management in access networks. The EPC is a split architecture network, where the user and signaling plans are separated and handled by different network entities. Important EPC 20 functionalities include the Home Subscriber Server (HSS) 26, a node that maintains a database containing the user and subscriber related information, and also is involved in session setup, authentication and authorization. The Serving Gateway (SGW) 24 is the gateway between the RAN 14 and the EPC 20, while the Packet Data Network Gateway (PGW) 28 connects the EPC 20 to external IP networks, such as the Internet 32 and IMS domain 40. PGW 28 includes IP address translation, and communicates with the Policy and Charging Rules Function (PCRF) 30. The Mobility Management Entity (MME) 22 is a signaling node, responsible for tracking and mobility of the UE 12 in the RAN 14.
An IP Multimedia Subsystem (IMS) domain 40 provides the control and media functions for voice and other real-time multimedia services in LTE networks 10. The IMS signaling protocol is the Session Initiation Protocol (SIP), which is standardized by the Internet Engineering Task Force (IETF). IMS 40 includes the Call Session Control Functions (P-CSCF 44, I-CSCF 48, and S-CSCF 46). The Proxy-CSCF (P-CSCF) 44 is a SIP proxy that is the first point of contact for the IMS domain 40. It acts as an anchor point to the IMS 40—encrypting and decrypting outgoing and incoming traffic, respectively. Interrogating-CSCF (I-CSCF) 48 is another IMS function serving as an edge node of the IP administrative domain. It includes a Domain Name System (DNS) address, enabling external servers to find the IMS system 40. Serving-CSCF (S-CSCF) 46 is a central SIP server performing session control and SIP registration. It connects the different SIP addresses and user profiles. Diameter protocol is used by S-CSCF 46 to obtain user profiles from HSS 26 in the EPC domain 40. Application Servers (AS) 52 host and control various services, such as voice, video, gaming, etc. An E.164 Number to URI Mapping (ENUM) node 50 translates telephone numbers into internet addresses. The ENUM 50 connects to a telephony AS providing various voice call services. Other networks may connect to the IMS domain 40, such as the Public Switched Telephone Network (PSTN) 34.
The complex network architecture and variety of network functionalities involved in providing multimedia services in mobile networks 10 require a performance monitoring and troubleshooting system that assures proper network operation and achievement of contracted services level. Such systems collect data from a variety of source, such as the network interfaces, terminals, and from the network node logs. In a mobile network 10, a very large amount of data is produced; therefore the management systems usually work on well selected data. Network nodes usually have performance management functions that are based on statistical counters. These contain time-aggregated data which may further be aggregated for other dimensions, cells, users, services, etc. Network nodes also generate event data in the form of streaming events or network logs. These contain more detailed information of the network operation. The active counters and events are configurable.
In the network interfaces, network probes generate an output of the protocol information. Performance monitoring systems collect this information. Since there are many network entities which are involved in the network operation, these data have to be collected and correlated from many network sources, in order to be able to obtain adequate information from end-to-end sessions or services.
Although counter based network management systems are suitable for high-level performance monitoring (PM), because they are based on statistical data, the details and individual problems are hidden. These systems are deficient for monitoring service levels of individual subscribers, and for troubleshooting.
In the case of event-based monitoring systems, the output is often time-aggregated, which has similar drawbacks to the counter-based systems. In case of failures, the call details are not available for detailed troubleshooting.
In many PM solutions, where data are available at the subscriber level, data for one user are correlated. The originating and terminating sides of calls, and PM data of the participating parties, are either not visible, or not correlated with each other in the output of the PM system.
Furthermore, most of the existing monitoring systems, even if they provide per-user information, only work within one domain (e.g., RAN 14, EPC 20, IMS 40, etc.) and do not perform cross-domain correlation. These systems can monitor and detect problems within a specific domain, but cannot map this information into end-to-end performance metrics due to a lack of information from other domains.
Using existing monitoring systems, network operators can collect cross-domain information, but they need to use multiple, (e.g., four to five) different monitoring solutions, and perform extensive manual “correlation like” steps to collect the information and put it in a useable form. Due to the extensive manual intervention, operators cannot apply their analysis for all of the customers; rather, it is limited to only certain specified users, such as drive testers. Furthermore, the typical delay in accessing and correlating this information is on the order of 30-45 minutes, at best.
The Background section of this document is provided to place embodiments of the present invention in technological and operational context, to assist those of skill in the art in understanding their scope and utility. Unless explicitly identified as such, no statement herein is admitted to be prior art merely by its inclusion in the Background section.